This invention relates in general to inflatable mattresses and cushions, and more particularly to an inflatable mattress or cushion having normally isolated zones and a series of valves for placing its normally isolated zones selectively in communication with each other and with atmosphere.
Those individuals who are confined to wheelchairs run the risk of tissue breakdown and the development of pressure sores, which are extremely dangerous and difficult to cure. Typically much of the individual's weight concentrates in the regions of the ischia, that is at the bony prominences of the buttocks, and unless frequent movement occurs, the flow of blood to the skin tissue in these regions decreases to the point that the tissue breaks down. Cushions which are especially designed for wheelchairs exist for reducing the concentration of weight in the region of the ischia, and these cushions generally seek to distribute the user's weight more uniformly over a larger area of the buttocks.
Cellular cushions provide the most uniform distribution of weight and thus provide the greatest protection from the occurrence of pressure sores. These cushions have an array of closely spaced air cells which project upwardly from a common base. Within the base the air cells communicate with each other, and thus all exist at the same internal pressure. Hence, each air cell exerts essentially the same restoring force against the buttocks, irrespective of the extent to which it is deflected. U.S. Pat. No. 4,541,136 shows a cellular cushion currently manufactured and sold by ROHO, Inc., of Belleville, Ill., for use on wheelchairs.
In a sense the typical cellular cushion provides a highly displaceable surface which tends to float the user. While this reduces the incidence of pressure sores, it detracts from the stability one usually associates with a seating surface. Most of those confined to wheelchairs have little trouble adjusting to the decrease in stability, but for those who have skeletal deformities, particularly in the region of the pelvis and thighs, and for those who lack adequate strength in their muscles, lesser stability can be a source of anxiety. A variation of the ROHO cellular cushion addresses this problem with totally isolated zones and also cells of varying height. By varying the pressure between zones, one can accommodate for skeletal deformities while still maintaining satisfactory protection against pressure sores. U.S. Pat. No. 4,698,864 shows a zoned cellular cushion with cells of varying height.
Typically, a zoned cellular cushion has a separate filling stem and valve for each of its zones. The user simply opens the valve of each stem and introduces air into the zone for that stem, usually with a hand pump, and then releases the air from the zones until the desired posture is achieved. In a more sophisticated arrangement, a hose kit connects a single pump to a manifold which in turn is connected to the several valves through separate hoses. These hoses are fitted with separate hose clamps so that the air from the pump may be directed to the cells of the individual zones independently, and likewise the air can be released from them independently, all by manipulating the clamps. The hoses of the hose kit lie externally of the cushion and may become entangled in components of a wheelchair. Furthermore, by reason of their remote location, the hose clamps are difficult to manipulate.
Even more traditional inflatable cushions derive advantages from zoning, that is from being divided into zones or compartments which can be isolated from each other to accommodate skeletal deformities.
Ser. No. 07/778,450 now U.S. Pat. No. 5,163,196, issued Nov. 17, 1992 describes a valve for a zoned inflatable cushion such that access to all of the zones is cut-off simultaneouly because the valve is in a flap which is part of the cushion base and all of the access channels run through the flap.
The present invention is an improvement on the prior cushions which utilize a series of hoses to inflate the cushion in that it positions the bodies of the hoses within the periphery of the cushion and gathers the ends of all of the hoses in close proximity adjacent to one edge so that they do not become entangled in the wheelchair and are readily accessible to the user. It also is an improvement on U.S. Pat. No. 5,163,196 in that the zones can be adjusted simultaneouly or selectively.
The present invention also resides in providing access to the cushion zones from beneath the cushion. A further advantage of the present invention is in providing access to the underside of the cushion and also to each cell of the cushion whereby pressure in each cell of the cushion can be monitored from a remote location.
This invention is equally appliable to inflatable mattresses, but will be described in connection with a wheelchair cushion.
These and other objects and advantages of the present invention will become apparent hereinafter.